Traditional Chinese fermented foods are favored by consumers due to their unique flavor, texture and nutritional values. A large number of microorganisms participate in the process of fermentation, especially lactic acid bacteria (LAB), which are present in almost all fermented foods and contribute to flavor development. The formation process of flavor is complex and involves the biochemical conversion of various food components. It is very important to fully understand the conversion process to direct the flavor formation in foods. A comprehensive link between the LAB community and the flavor formation in traditional Chinese fermented foods is reviewed. The main mechanisms involved in the flavor formation dominated by LAB are carbohydrate metabolism, proteolysis and amino acid catabolism, and lipolysis and fatty acid metabolism. This review highlights some useful novel approaches for flavor enhancement, including the application of functional starter cultures and metabolic engineering, which may provide significant advances toward improving the flavor of fermented foods for a promising market.

This study investigated the impact of ultrasound-assisted immersion freezing (UIF), air freezing (AF), and immersion freezing (IF) on the ice crystal size, protein thermal stability, and physicochemical properties of common carp (Cyprinus carpio) muscle during frozen storage. UIF samples had smaller ice crystals throughout the storage period than AF and IF samples did, which led to less damage to the muscle tissue. Low-field nuclear magnetic resonance analysis revealed that UIF reduced the mobility and loss of immobilized and free water. The thawing and cooking losses in the UIF samples were significantly lower than those in the IF and AF samples (P < 0.05). The AF samples had a higher shear force (P < 0.05) than UIF and IF samples did at the beginning of storage, and then the shear force reduced rapidly. During the 90-180 days, the shear force of the UIF samples was higher than that of the AF and IF samples (P < 0.05). Decreases in the Tmax and enthalpies were observed for all of the treatments during storage, and the UIF samples had a higher protein thermal stability than AF and IF samples did. The UIF samples showed lower thiobarbituric acid reactive substance and total volatile basic nitrogen values during storage than the AF and IF samples did (P < 0.05). Principal component analysis showed that there were significant correlations between the freezing methods and the ice crystal size, protein thermal stability and physicochemical characteristics of frozen muscles. Overall, UIF was an effective way to inhibit the deterioration of frozen fish during frozen storage.